1. Field of the Invention
The present invention relates to medical instruments and, in particular, a system and method for placing a cannula through tissue.
2. Prior Art
Culdoscopy is a well known medical procedure for visualization of the pelvic organs by means of an optical instrument through the vaginal route. In the past a relatively large trocar was used to pierce through the peritoneum wall. However, because of the close proximity of the colon and the uterus and because of the relatively large size of the trocar, a surgeon could inadvertently penetrate into or damage the uterus or colon. Precise positioning of the trocar was not always consistent. The present invention is intended to overcome these problems and provide an easier to use and more consistently precise system.
Culdoscopy was abandoned in the 1970s as laparoscopy provided a panoramic view of the pelvis and was shown to be superior for tubal sterilization. Difficulties and complications of culdoscopic sterilization were, however, associated with visualization and exteriorisation of the tube. The advantages of culdoscopy in infertility were stressed in the French and English literature. While the technology of laparoscopy was continuously improved the technique of culdoscopy did not advance after the 1960s.
Diagnostic laparoscopy as a standard procedure in the investigation of infertility is frequently performed in healthy women without obvious pelvic pathology resulting in normal findings or pathology of doubtful clinical significance. Unfortunately, laparoscopy is not innocuous and should be considered as a major surgical procedure. For these reasons the procedure is frequently postponed in asymptomatic patients until a later stage in the investigation process, and repeat procedures to evaluate the evolution of disease or to check the effect of treatment are not considered routine clinical practice. Minilaparoscopy is likely to be more acceptable by avoiding general anesthesia. However, the access from the umbilicus used in laparoscopy does not give the ideal angle for inspecting the tubo-ovarian structures. To expose the full ovarian surface and fossa ovarica several steps are required such as Trendelenburg position, distension by CO.sub.2 pneumoperitoneum, insertion of a second trocar and manipulation of bowel and adnexa. The CO.sub.2 pneumoperitoneum provokes patient's discomfort and the acidosis is potentially harmful to the patient and, where intrafallopian transfer procedures are involved, to gametes and embryos. Concern has also been expressed that growth and spread of tumor cells may be accelerated by laparoscopy with air or CO.sub.2. Finally, structures such as fimbriae and avascular adhesions are easier to inspect by hydroflotation than with a pneumoperitoneum. The use of saline as the distension medium in diagnostic laparoscopy is attractive but impracticable with the patient in the Trendelenburg position.